Anti-whaling group Sea Shepherd expects the Japanese whaling fleet to begin its annual hunt by the end of the week.

The crew on board the Steve Irwin found the whaling factory ship earlier this week by using a military-style drone.

Sea Shepherd's Paul Watson says they intercepted the fleet earlier than last year and will now keep the chase up.

He says it is now a task of following the Nisshin Maru to its destination in the Southern Ocean.

"Right now it's just a chase and hopefully once we get there it'll continue to be the chase because last year we kept them on the run for 3,000 miles all the way to the tip of South America," he said.

"So hopefully we can keep them on the run again.

"It will be about the last day of the month that they'll be in a position, about December 31st, that they'll be in a position to actually go whaling and that's when we'll be find some confrontation happening."